A great way to jazz up the “gray” of an over-cast day, is to use this technique I learned from legendary sports photographer, Dave Black.
I switched my Nikon D3 white balance setting to tungsten. And I under-expose the background by a stop or more. This switches the gray sky to a moody blue tone. Then I placed full CTO (orange) gels on two Nikon SB-800 speedlights, effectively turning them into tungsten-balanced lights. This brings the light temperature from the flashes back to a natural color. I fired my remote flashes using an SB-900 on the camera, set to Master, and triggered them with my RadioPopper Px system. One flash was up high on a Bogen lightstand. The other was rimming from behind on a Bogen Justin Clamp.
No crazy Photoshop here…this was all done “in-camera”! 🙂